Waves 1

Question 1

Define a longitudinal wave

Answer 1

a wave where the plane of oscillation of particles is parallel to the direction of energy propagation

Question 2

Give two examples of longitudinal waves

Answer 2

1) sound waves

2) P-waves

Question 3

Define a transverse waves

Answer 3

a wave where the plane of oscillation of particles is perpendicular to the direction of energy propagation

Question 4

Give two examples of transverse waves

Answer 4

1) EM waves
2) water waves
3) S-waves

Question 5

Define a progressive wave

Answer 5

a moving wave that carries energy from one place to another without transferring any matter

Question 6

Define the amplitude of a wave

Answer 6

the maximum displacement of the wave from equilibrum

Question 7

Define wavelength

Answer 7

the shortest distance between two points in phase

Question 8

Define time period

Answer 8

the time taken for one whole wavelength to pass a point

Question 9

Define frequency

Answer 9

the number of whole wave cycles passing a given point per second

Question 10

Define a polarised wave

Answer 10

a wave in which all the vibrations are in one plane, perpendicular to its direction of propagation

Question 11

Define polarisation

Answer 11

restricting a wave’s oscillations to one plane, perpendicular to its direction of propagation

Question 12

How do you show an unpolarised wave in a drawing?

Answer 12

1) an up and down arrow with a dot in the middle

OR

2) arrows going all directions out from the centre

Question 13

How do you show a polarised wave in a drawing?

Answer 13

an up and down arrow

Question 14

Define phase

Answer 14

a measurement of the position of a certain point on a wave cycle (measured as an angle or in fractions of a cycle)

Question 15

Define phase difference

Answer 15

the amount by which one wave lags behind another (measured as an angle or in fractions of a cycle)

Question 16

If two points are in phase, what is their phase difference?

Answer 16

0

Question 17

If two points are in antiphase, what is there phase difference?

Answer 17

π radians

Question 18

When does superposition occur?

Answer 18

• when two (or more) waves overlap/interfere

- the resultant wave is the sum of the displacements of the original waves

Question 19

What are the two types of interference?

Answer 19

1) constructive

2) destructive

Question 20

When does constructive interference occur?

Answer 20

when two waves are in phase

Question 21

When does destructive interference occur?

Answer 21

when two waves are in antiphase

Question 22

Define a stationary/standing wave

Answer 22

• a wave formed when two progressive waves travelling in opposite directions superposition
• their wavelengths (and frequencies) must be equal and their amplitudes similar

Question 23

What must the length of the string equal in terms of λ in order for a standing wave to be seen?

Answer 23

length = (nλ)/2

n = 1, 2, 3, …

Question 24

Define a node

Answer 24

a point of minimum amplitude on a standing wave

Question 25

Define an antinode

Answer 25

a point of maximum amplitude on a standing wave

Question 26

How do you represent an antinode?

Answer 26

x

Question 27

How do you represent a node?

Answer 27

.

Question 28

Is there energy transfer in a standing wave?

Answer 28

no

energy is stored

Question 29

What does μ equal in the equation: f=(1/2l)x√(t/μ)?

Answer 29

mass per unit length

Question 30

What does l equal to in the equation: f=(1/2l)x√(t/μ)?

Answer 30

distance between outermost nodes

Question 31

List 5 properties of a standing wave

Answer 31

1) no energy transfer along the wave
2) internodal distance = λ/2
3) points between two adjacent nodes are all in phase
4) points between two adjacent nodes are in antiphase with the points between the neighboring adjacent nodes
5) a whole number of (λ/2)s fit onto the string